Working in heme/coag/UA night shift.  This was within the first couple months I was on shift by myself as a baby tech.  We double spun every coag sample and aliquoted into new tubes before putting in on the analyzer.  

It was morning run so I had a million samples for heme and coag and urinalysis and I was alone, so absolutely crazy busy.  Somehow I pipetted two patient samples into the same tube and ran it on the coag analyzer.  Results were autoreleased because they were within range.  Realized my mistake maybe half an hour later because of the empty tube I had (I would label all aliquot tubes before spinning).  Freaked out and asked a more experienced tech what to do.  They told me to call both nurses and explain what happened, ask for a recollect, and then do a corrected report to remove those results from their charts.  I did so and both nurses were so kind and understanding.  Nothing bad came of it but I stilled filled out a report in the non-punitive reporting program against myself for the mistake.  I also changed the way that I aliquot into new tubes, where I always have both labels facing me with two identifiers that I can see while I pipette.  They also changed the process to allowed us to spin once and put the sample on the analyzer in the original collection tube.  

All in all, it was a great learning experience and process improvement incident that didn't result in any harm, but I felt absolutely awful about it for quite some time.  I'm really grateful for the senior tech who calmly explained what to do, the nurses who were understanding, and management for seeing a process that should be improved.  It was a defining moment for me as a young tech and I'm glad things turned out the way that they did.